Final report for a brushless dc torque motor

Brushless direct current torque motor using permanent magnet rotor and three-phase winding in stationary armature for operation in vacuu

Brushless d.c. torque motor first quarterly report, 25 jun. - 25 sep. 1964

Brushless direct current torque moto

Evaluation of ignition mechanisms in selected spacecraft materials Final report, 1 Mar. - 30 Jun. 1967

Evaluation of ignition mechanisms for spacecraft materials in simulated spacecraft cabin atmosphere

An advanced brushless dc torque motor Quarterly report, 30 Sep. - 30 Dec. 1966

Design of torque motor controller, and operation of breadboard control circui

Density-functional investigation of the rhombohedral to simple cubic phase transition of arsenic

We report on our investigation of the crystal structure of arsenic under compression, focusing primarily on the pressure-induced A7 to simple cubic (sc) phase transition. The two-atom rhombohedral unit cell is subjected to pressures ranging from 0 GPa to 200 GPa; for each given pressure, cell lengths and angles, as well as atomic positions, are allowed to vary until the fully relaxed structure is obtained. We find that the nearest and next-nearest neighbor distances give the clearest indication of the occurrence of a structural phase transition. Calculations are performed using the local density approximation (LDA) and the PBE and PW91 generalized gradient approximations (GGA-PBE and GGA-PW91) for the exchange-correlation functional. The A7 to sc transition is found to occur at 21+/-1 GPa in the LDA, at 28+/-1 GPa in the GGA-PBE and at 29+/-1 GPa in the GGA-PW91; no volume discontinuity is observed across the transition in any of the three cases. We use k-point grids as dense as 66X66X66 to enable us to present reliably converged results for the A7 to sc transition of arsenic.Comment: To be published in Physical Review B; material supplementary to this article is available at arXiv:0810.169

Fermi-surface calculation of the anomalous Hall conductivity

While the intrinsic anomalous Hall conductivity is normally written in terms of an integral of the electronic Berry curvature over the occupied portions of the Brillouin zone, Haldane has recently pointed out that this quantity (or more precisely, its ``non-quantized part'') may alternatively be expressed as a Fermi-surface property. Here we present an {\it ab-initio} approach for computing the anomalous Hall conductivity that takes advantage of this observation by converting the integral over the Fermi sea into a more efficient integral on the Fermi surface only. First, a conventional electronic-structure calculation is performed with spin-orbit interaction included. Maximally-localized Wannier functions are then constructed by a post-processing step in order to convert the {\it ab-initio} electronic structure around the Fermi level into a tight-binding-like form. Working in the Wannier representation, the Brillouin zone is sampled on a large number of equally spaced parallel slices oriented normal to the total magnetization. On each slice, we find the intersections of the Fermi-surface sheets with the slice by standard contour methods, organize these into a set of closed loops, and compute the Berry phases of the Bloch states as they are transported around these loops. The anomalous Hall conductivity is proportional to the sum of the Berry phases of all the loops on all the slices. Illustrative calculations are performed for Fe, Co and Ni.Comment: 12 pages, 9 figure

Reusing Data and Metadata to Create New Metadata Through Machine-Learning & Other Programmatic Methods

Recent improvements in natural language processing (NLP) enable metadata to be created programmatically from reused original metadata or even the dataset itself. Transfer-learning applied to NLP has greatly improved performance and reduced training data requirements. In this talk, well compare machine-generated metadata to human-generated metadata and discuss characteristics of metadata and data archives that affect suitability for machine-learning reuse of metadata. Where as human-generated metadata is often populated once, populated from the perspective of data supplier, populated by many individuals with different words for the same thing, and limited in length, machine-generated metadata can be updated any number of times, generated from the perspective of any user, constrained to a standardized set of terms that can be evolved over time, and be any length required. Machine-learning generated metadata offers benefits but also additional needs in terms of version control, process transparency, human-computer interaction, and IT requirements. As a successful example, well discuss how a dataset of abstracts and associated human-tagged keywords from a standardized list of several thousand keywords were used to create a machine-learning model that predicted keyword metadata for open-source code projects on code.nasa.gov. Well also discuss a less successful example from data.nasa.gov to show how data archive architecture and characteristics of initial metadata can be strong controls on how easy it is to leverage programmatic methods to reuse metadata to create additional metadata

Analysis of nuclear waste disposal in space, phase 3. Volume 1: Executive summary of technical report

The objectives, approach, assumptions, and limitations of a study of nuclear waste disposal in space are discussed with emphasis on the following: (1) payload characterization; (2) safety assessment; (3) health effects assessment; (4) long-term risk assessment; and (5) program planning support to NASA and DOE. Conclusions are presented for each task

Analysis of nuclear waste disposal in space, phase 3. Volume 2: Technical report

The options, reference definitions and/or requirements currently envisioned for the total nuclear waste disposal in space mission are summarized. The waste form evaluation and selection process is documented along with the physical characteristics of the iron nickel-base cermet matrix chosen for disposal of commercial and defense wastes. Safety aspects of radioisotope thermal generators, the general purpose heat source, and the Lewis Research Center concept for space disposal are assessed as well as the on-pad catastrophic accident environments for the uprated space shuttle and the heavy lift launch vehicle. The radionuclides that contribute most to long-term risk of terrestrial disposal were determined and the effects of resuspension of fallout particles from an accidental release of waste material were studied. Health effects are considered. Payload breakup and rescue technology are discussed as well as expected requirements for licensing, supporting research and technology, and safety testing

Subsonic aerodynamic and flutter characteristics of several wings calculated by the SOUSSA P1.1 panel method

The SOUSSA (steady, oscillatory, and unsteady subsonic and supersonic aerodynamics) program is the computational implementation of a general potential flow analysis (by the Green's function method) that can generate pressure distributions on complete aircraft having arbitrary shapes, motions and deformations. Some applications of the initial release version of this program to several wings in steady and oscillatory motion, including flutter are presented. The results are validated by comparisons with other calculations and experiments. Experiences in using the program as well as some recent improvements are described